Some medical treatments involve the use of a medical catheter with a distal anchor that retains the catheter in position in the body of a patient. Some treatments use a drainage catheter. For example, procedures for the suprapubic catheterization of the bladder drain the bladder after surgery or when an obstruction plugs the genitourinary system. Percutaneously inserted catheters can also drain the kidneys, biliary system, abscesses, other sites of fluid collection and other viscera. As an alternative to providing drainage, percutaneously inserted catheters can introduce substances into the patient's body such a fluids introduced through gastrostomy feeding tubes.
Since body movements can inadvertently lead to catheter displacement, various anchoring mechanisms have been developed. For example, a Foley bladder catheter includes an inflatable balloon at the distal end, an inflation channel in the walls of the catheter, an external supply of inflation fluid connected to the channel and a valve to keep the fluid in place and the balloon inflated.
Alternatively, the distal end of the catheter can include a “pigtail loop” formed from a flexible tube. Typically, the pigtail loop is preformed from a shape-memory material. For introduction into a patient, a physician inserts a stiff cannula or stylet into the catheter lumen to straighten the pigtail loop. The distal end of the flexible tube returns to the pigtail configuration after the physician removes the cannula. In some cases, return to the pigtail configuration may be aided or secured by the use of a suture thread that extends through draw ports at two spaced positions on the flexible tube. These draw ports move toward each other when the physician removes the cannula. The physician can then take up slack and secure the pigtail by applying tension to the suture thread. To remove the catheter, the physician can reverse the above procedures.
Other anchor mechanisms include malecots with “wings” or “arms” in a distal portion of the catheter wall. The application of force to a distal tip of the catheter can expand the wings, and the wings extend outward protruding radially to create an anchor for the catheter. The force can be applied by pulling on a suture string or a rod extending through the lumen of the catheter. Alternatively, the wings of the malecot can be formed from a shape-memory material with a naturally protruding configuration, and a stylet is used to push the distal end of the catheter and collapse the malecot.